Device for preventing development of non-image marginal portions of a photoreceptor in electrophotographic copying apparatus

ABSTRACT

In an electrophotographic copying apparatus, a device for preventing the charging device from charging selected marginal portions of a photoreceptor, to thereby prevent staining of these selected marginal portions when the charged part of the photoreceptor is exposed to the image of an original, and this image is later developed. Charging of the selected marginal portions of the photoreceptor is prevented by means of plates which are moved with respect to the charging device by manually moving indicators disposed along the length and width of the rest plate that supports an original for copying. Thus, only that portion of the photoreceptor which corresponds to the selected size of the original is charged, while the marginal portions of the photoreceptor which would surround the projected image of the original are not charged.

United States Patent 1191 1111 3,827,799 Koizumi Aug. 6, 1974 [54] DEVICE FOR PREVENTING 3,671,121 6/1972 1156" 355/3 R x DEVELOPMENT OF NONJMAGE 3,685,895 8/1972 Wright et al. 355/3 R 3,724,940 4/1973 Yutaka K012111111 355/3 R MARGINAL PORTIONS OF A 3,751,155 8/1973 Liechty 355/125 x PHOTORECEPTOR IN ELECTROPHOTOGRAPHIC COPYING APPARATUS Inventor: Yutaka Koizumi, Yokohama, Japan Assignee: Ricoh Co., Ltd., Tokyo, Japan Filed: Apr. 5, 1973 Appl. No.: 348,228

Foreign Application Priority Data Apr. 17, 1972 Japan 47-37745 References Cited UNITED STATES PATENTS l/197l Lux et al 355/55 5/1971 Michaud et al. 317/262 A UX 9/l97l Metcalfe et al 317/262 A 4/1972 Kakii et al. 355/13 Primary ExaminerSamuel S. Matthews Assistant Examiner-Kenneth C. Hutchison Attorney, Agent, or Firm-Cooper, Dunham, Clark, Griffin & Moran [5 7] ABSTRACT In an electrophotographic copying apparatus, a device for preventing the charging device from charging selected marginal portions of a photoreceptor, to thereby prevent staining of these selected marginal portions when the charged part of the photoreceptor is exposed to the image of an original, and this image is later developed. Charging of the selected marginal portions of the photoreceptor is prevented by means of plates which are moved with respect to the charging device by manually moving indicators disposed along the length and width of the rest plate that supports an original for copying. Thus, only that portion of the photoreceptor which corresponds to the selected size of the original is charged, while the marginal portions of the photoreceptor which would surround the projected image of the original are not charged.

5 Claims, 2 Drawing Figures DEVICE FOR PREVENTING DEVELOPMENT OF NON-IMAGE MARGINAL PORTIONS OF A PHOTORECEPTOR IN ELECTROPHOTOGRAPI-IIC COPYING APPARATUS BACKGROUND OF THE INVENTION The invention relates to a device for preventing staining of marginal portions of a photoreceptor in an electrophotographic copying apparatus.

When pages of a book, for example, are copied by an electrophotographic copying apparatus, stains are often produced in the marginal portions of the duplicates, and the appearance of the duplicates is poor. Thus, it is often desirable or required to retouch the duplicate in order to remove the marginal stain thereon, particularly when the duplicates are intended for use as master plates for offset printing.

In prior art electrophotographing processes of the dry developing type, it has been customary to withdraw from the copying machine a copy sheet which is developed, but not yet fixed in order to clean off toner particles from the marginal portions of the copy sheet. In electrophotographic processes of the wet developing type, it has been customary to retouch by applying a hydrophilic liquid to selected portions of a copy sheet. The prior art retouching method for the dry developing type copy sheets is effective, but is time consuming. The retouching method for the wet developing type copy sheets is time consuming and additionally is not very effective. It is desirable therefore to improve the appearance of photoreceptors, such as copy sheets, by conveniently and effectively preventing staining of marginal portions thereof.

SUMMARY OF THE INVENTION An object of the invention is to provide a device which prevents staining of marginal portions of a photoreceptor and thus obviates the need to retouch a photoreceptor after it has been charged and exposed to an image of an original.

This object is accomplished by providing charge preventing plates which are movably disposed adjacent the charging device of an electrophotographing copying apparatus and can prevent charging of marginal portions of the photoreceptor on which portions no image of the original is projected. The copying apparatus is provided with a width indicator mounted for sliding movement along an edge of theoriginal rest glass plate of the apparatus, and the width indicator is linked with a pair of charge preventing plates whose position with respect to the width of the photoreceptor can be adjusted by manually moving the width indicator. Additionally, a length indicator is provided along another edge of the original rest glass plate, and is linked with a light intercepting plate provided at least at one of the two longitudinal ends of the exposing device of the copying machine. The light intercepting plate is provided with a light source for illuminating a marginal area of the photoreceptor on which no image of the original is projected, so that the charge carried by such marginal area can be removed. The longitudinal portion of the photoreceptor on which an image will be projected may thus be selected by manually moving the length indicator along the orignal rest glass plate.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an electrophotographic copying apparatus incorporating the. invented device for preventing staining of marginal portions of a photoreceptor.

FIG. 2 is a perspective partial view of a charging device forming apart of the apparatusshown in FIG. 1.

DETAILED DESCRIPTION In FIG. 1, a book 2 is placed on an original rest glass plate 1 of an electrophotographing copying apparatus. The apparatus includes a charging device 3, an exposing device 4 and a developing device 5 which are disposed along the same horizontal plane in the indicated order. A lens system 7 is interposed between the original glass plate 1 and the exposing device 4. A photoreceptor 8 is suitably fed in the indicated direction.

For the purpose of selectively preventing the charging of side marginal portions of the photoreceptor 8, the charging device 3 includes a pair of charge preventing plates 9 and 9A each disposed at one of the transverse ends of the charging device 3-for sliding movement in a direction transverse to the direction of movement of the photoreceptor 8a The plates 9 and 9A are urged inwardly, toward each other, by means of return springs 10 and 10A respectively.

For the purpose of selectingthe desired width of the original, the original rest glass plate 1 is graduated at its edge 11, and two indicators 12 and 12Aare suitably mounted along the edge 11 so that they can be manually moved slidably therealong. Thev indicator l2 and 12A are linked with the charge preventing plates 9 and 9A respectively through respective strings l8 and 18A and suitable pulleys. The link is such that when the indicators l2 and 12A are moved along the graduations at the edge 11 of the original rest glass plate 1, the charge preventing plate 9 and 9A move under or against the biasing force of the spring 10 and 10A toward or away from each other. Each of the charge preventing plates 9 and 9A may thus be moved independently.

For the purpose of preventing undesirable staining of the longitudinal marginal portions of the photoreceptor 8, an upstanding light intercepting plate 14 is disposed at the longitudinal end of the exposing device 4 which is adjacent the charging device 3. The light intercepting plate l4-is mounted on horizontal shafts l5 and 15A for longitudinal sliding movement. The light intercepting plate 14 includes an upper marginal portion 14A which is bent horizontally to point towards the charging device 3. An electric lamp 16 is suitably secured to the side of the intercepting plate 14 which faces the charging device 3 and is disposed below the. horizontally bent upper marginal portion 14A. When a photoreceptor 8 is disposed at the exposing station 4, and the lamp 16 is on, the bottom marginal portion of the photoreceptor is illuminated by the lamp 16 to thereby remove the electric charge thereon.

For the purpose of selecting the longitudinal size, of the charging portion of a photoreceptor 8, the original rest glass plate 1 is provided with a length indicator 18 mounted along an edge of the plate 1 which is transverse to the edge 11. The length indicator 18 is linked with the plate 14 by means of a string. 19 and suitable 3 pulleys, and a spring 17 is provided to urge the plate '14 toward the charging device 3.

The invented device operates as follows: When an original 2 is placed over the original rest glass plate 1, as shown in: FIG. 1, the width indicators 12 and 12A are manually moved to indicate the desired width of the original. The manual movement of the width indicators 12 and 12A moves, through the strings 13 and 13A respectively, the chargepreventing plates and 10A respectively, such that the distance between the charge preventing plates 10 and 10A corresponds to the distance between the indicators 12 and 12A and hence to the desired width of the original 2.

The length indicator 18 is manually moved to indicate the desired length of the original 2. As the length indicator is moved, the light intercepting plate 14 moves correspondingly, because of the link through the string 19, to a selected position with respect to the exposing station 4.

A photoreceptor 8 is then moved, by conventional means, in the indicated direction such that its side marginal portions are between the charging device 3 and 'the charge preventing plates 9 and 9A. As the photoreceptor 8 moves under the charging device 3, the portions thereof which are between the charge preventing plates 9 and 9A are electrically charged in the conventional manner, while the side marginal portions which are above the charge preventing plates 9 and 9A are not so charged.

The photoreceptor 8 moves into the exposing device 4 and is conventionally stopped at an exposing position by suitable means including a microswitch for detecting the proper exposing position of the photoreceptor 8.

After the photoreceptor 8 is in its exposing position, it is exposed to an optical image of the original 2 by conventional means to thereby form on the photoreceptor 8 an electrostatic latent image of the original 2. At the same time, or immediately after the photoreceptor 8 is exposed to the image of the original, the lamp 16 is turned on by suitable means, such as by the closing of the microswitch 20, to thereby illuminate the bottom marginal portion of the photoreceptor 8 and to remove the charge therefrom.

It should be clear that the intercepting plate 14 may be disposed at the end of the exposing device 4 which is away from the charging device 3, such that it can selectively illuminate a top marginal portion of a photoreceptor 8 which is at the exposing position. It should also be clear that similar intercepting plates 14 may be disposed at each of the two longitudinal ends of the exposing station 4, such that both the top and the bottom margins of a photoreceptor 8 may be illuminated. When two intercepting plates 14 are used, a second length indicator, similar to the shown length indicator 18, may be provided and may be linked with the second intercepting plate 14 in a manner similar to the manner in which the length indicator 18 is linked to the shown intercepting plate 14. The arrangement of two length indicators 18 may be similar to the arrangement of the shown width indicators 12 and 12A.

After the photoreceptor is exposed as aforementioned, it is conventionally moved through a developing device 5, and a fixing device 6 before being discharged from the copying apparatus. Since the selected marginal portions of thephotoreceptor 8 are not electrically charged, they are not stained by toner particles or otherwise in the course of developing the image projected thereon.

The invented device is useful for preventing staining of selected marginal portions of a photoreceptor in electrophotographic copying apparatus both of the dry developing type and of the wet developing type. It obviates the prior art need for retouching duplicates, and provides duplicates which are commercially acceptable and have pleasing appearance. The waste of developing agent which is associated with prior art methods is minimized. Additionally, the invented device is beneficial to the operator of a copying machine and to the general appearance of the premises of a copying machine because it prevents scattering of toner particles occasioned by retouching.

Since it is not required to remove a duplicate from the machine for retouching before the toner image is fixed, the space required for prior art retouching is eliminated, and thus the size of the premises necessary for copying is minimized and production speed is increased.

When subjecting a portion of a photoreceptor to multiple exposure, or multiple transfer printing, it has been customary to cover selected portions of the original with a white frame. The invented device eliminates the use of such white frames on such occassions, and speeds up multiple exposure or multiple transfer printing processes.

I claim:

1. A device for preventing staining of selected marginal portions of a photoreceptor in an electrophotographic copying apparatus including means for charing a photoreceptor moving along a defined path with respect to the charging means, said device comprising a plurality of charge preventing plates and means for se lectively positioning said plates at the side margins transversely of said path to prevent charging of selected side marginal portions of the photoreceptor by the charging means and to thereby define the width of the charged area of the photoreceptor, an original rest plate for supporting an original for copying, width indicator means, means for mounting the width indicator means for sliding movement along one edge of the rest plate transverse to said defined path to indicate the desired width of an original placed on the plate, means for supporting the charge preventing plates for sliding transverse movement with respect to the charging means, and means for linking the indicator means with the charge preventing plates for corresponding movement thereof when the width indicator means are manually moved to indicate the desired width of an original.

2. A device as in claim 1 wherein the photocopying machine includes an exposing station having an exposing position along the path of the photoreceptor downstream from the charging means and means for projecting an image of an original supported on said rest plate onto a photoreceptor at an exposing position at said exposing station, said device comprising, at least at one of the longitudinal ends of the exposing station along the path of the photoreceptor, a light intercepting plate extending transversely to the path of the photoreceptor and having a light source on the side facing away from the exposing station to illuminate a selected margin at a longitudinal end of a photoreceptor in the exposing position, whereby the light source may be selectively turned on to illuminate and thereby discharge a selected charge marginal portion at a longitudinal end of a photoreceptor.

3. A device as in claim 2 including means for supporting the light intercepting plate for longitudinal movement toward and away from the exposing station, length indicator means, means for mounting the length indicator means for sliding movement along a longitudinal edge of the rest plate to indicate the desired length of an original placed on the plate, and means for linking the length indicator means with the support means for the light intercepting plate for corresponding movement of the light intercepting plate when the length indicator means are moved manually to indicate the desired length of an original.

4. A device for preventing staining of selected marginal portions of a photoreceptor in an electrophotographying copying apparatus including means for charging a photoreceptor moving along a defined path with respect to the charging means, said device comprising a plurality of charge preventing plates and means for selectively positioning said plates at the side margins transversely of said path to prevent charging of selected side marginal portions of the photoreceptor by the charging means and to thereby define the width of the charged area of the photoreceptor, said machine further including an exposing station having an exposing position along the path of a photoreceptor downwstream from the charging means, and means for projecting an image of an original onto a photoreceptor at an exposing position at said exposing station, said device further comprising means for selectively discharging a marginal portion at least at one of the longitudinal ends of a photoreceptor at the exposing position including a light source and a light intercepting plate blocking the light therefrom and preventing it from reaching a selected central portion of the photoreceptor at the exposing position, a width indicator and a length indicator each slidably mounted along a different one of two intercepting edges of the original rest plate and manually moveable therealong to indicate the desired width and length of an original respectively, and means for linking said indicators with the charge preventing plates and with the light intercepting plate respectively to position the plates for discharging of marginal portions of a photoreceptor surrounding the area of the photoreceptor corresponding to the selected desired size of an original.

5. A device for preventing staining of selected marginal portions of a photoreceptor in an electrophotographic copying apparatus having means for charging a photoreceptor moving along a defined path with respect to the charging means, an original rest plate for supporting an original placed thereon for copying and exposing means having an exposing station located downstream from the charging means along the path of the photoreceptor for projecting an image of an original placed on the rest plate for copying onto a photoreceptor disposed at an exposing position at said exposing station, said device comprising moveable means disposed adjacent the charging means for selectively preventing the charging of selected side marginal portions of a photoreceptor moving towards the exposing means and means located at least at one of the longitudinal ends of the exposing means for discharging selected marginal portions at least at one of the longitudinal ends of a photoreceptor disposed at the exposing position, a width indicator visible from outside the copying apparatus and mounted for sliding movement along an edge of the rest plate transverse to said defined path and a length indicator visible from outside the copying apparatus and mounted for sliding movement along a longitudinal edge of the rest plate parallel to said defined path, means for linking the width indicator with the charge preventing means for moving the charge preventing means to a position for preventing the charging of selected side marginal portions of the photoreceptor as indicated by the position to which the width indicator has been moved, and means for linking the discharging means at the exposing station with the length indicator for discharging a selected marginal portion of the photoreceptor at its exposing position as indicated by the position to which the length indicator has been moved. 

1. A device for preventing staining of selected marginal portions of a photoreceptor in an electrophotographic copying apparatus including means for charing a photoreceptor moving along a defined path with respect to the charging means, said device comprising a plurality of charge preventing plates and means for selectively positioning said plates at the side margins transversely of said path to prevent charging of selected side marginal portions of the photoreceptor by the charging means and to thereby define the width of the charged area of the photoreceptor, an original rest plate for supporting an original for copying, width indicator means, means for mounting the width indicator means for sliding movement along one edge of the rest plate transverse to said defined path to indicate the desired width of an original placed on the plate, means for supporting the charge preventing plates for sliding transverse movement with respect to the charging means, and means for linking the indicator means with the charge preventing plates for corresponding movement thereof when the width indicator means are manually moved to indicate the desired width of an original.
 2. A device as in claim 1 wherein the photocopying machine includes an exposing station having an exposing position along the path of the photoreceptor downstream from the charging means and means for projecting an image of an original supported on said rest plate onto a photoreceptor at an exposing position at said exposing station, said device comprising, at least at one of the longitudinal ends of the exposing station along the path of the photoreceptor, a light intercepting plate extending transversely to the path of the photoreceptor and having a light source on the side facing away from the exposing station to illuminate a selected margin at a longitudinal end of a photoreceptor in the exposing position, whereby the light source may be selectively turned on to illuminate and thereby discharge a selected charge marginal portion at a longitudinal end of a photoreceptor.
 3. A device as in claim 2 including means for supporting the light intercepting plate for longitudinal movement toward and away from the exposing station, length indicator means, means for mounting the length indicator means for sliding movement along a longitudinal edge of the rest plate to indicate the desired length of an original placed on the plate, and means for linking the length indicator means with the support means for the light intercepting plate for corresponding movement of the light intercepting plate when the length indicator means are moved manually to indicate the desired length of an original.
 4. A device for preventing staining of selected marginal portions of a photoreceptor in an electrophotographying copying apparatus including means for charging a photoreceptor moving along a defined path with respect to the charging means, said device comprising a plurality of charge preventing plates and means for selectively positioning said plates at the side margins transversely of said path to prevent charging of selected side marginal portions of the photoreceptor by the charging means and to thereby define the width of the charged area of the photoreceptor, said machiNe further including an exposing station having an exposing position along the path of a photoreceptor downwstream from the charging means, and means for projecting an image of an original onto a photoreceptor at an exposing position at said exposing station, said device further comprising means for selectively discharging a marginal portion at least at one of the longitudinal ends of a photoreceptor at the exposing position including a light source and a light intercepting plate blocking the light therefrom and preventing it from reaching a selected central portion of the photoreceptor at the exposing position, a width indicator and a length indicator each slidably mounted along a different one of two intercepting edges of the original rest plate and manually moveable therealong to indicate the desired width and length of an original respectively, and means for linking said indicators with the charge preventing plates and with the light intercepting plate respectively to position the plates for discharging of marginal portions of a photoreceptor surrounding the area of the photoreceptor corresponding to the selected desired size of an original.
 5. A device for preventing staining of selected marginal portions of a photoreceptor in an electrophotographic copying apparatus having means for charging a photoreceptor moving along a defined path with respect to the charging means, an original rest plate for supporting an original placed thereon for copying and exposing means having an exposing station located downstream from the charging means along the path of the photoreceptor for projecting an image of an original placed on the rest plate for copying onto a photoreceptor disposed at an exposing position at said exposing station, said device comprising moveable means disposed adjacent the charging means for selectively preventing the charging of selected side marginal portions of a photoreceptor moving towards the exposing means and means located at least at one of the longitudinal ends of the exposing means for discharging selected marginal portions at least at one of the longitudinal ends of a photoreceptor disposed at the exposing position, a width indicator visible from outside the copying apparatus and mounted for sliding movement along an edge of the rest plate transverse to said defined path and a length indicator visible from outside the copying apparatus and mounted for sliding movement along a longitudinal edge of the rest plate parallel to said defined path, means for linking the width indicator with the charge preventing means for moving the charge preventing means to a position for preventing the charging of selected side marginal portions of the photoreceptor as indicated by the position to which the width indicator has been moved, and means for linking the discharging means at the exposing station with the length indicator for discharging a selected marginal portion of the photoreceptor at its exposing position as indicated by the position to which the length indicator has been moved. 